JP5565021B2 - Welding wire feed guide, submerged arc welding machine, and UOE steel pipe manufacturing method - Google Patents

Description

  The present invention relates to a welding wire feed guide, a multi-electrode submerged arc welding machine using the same, and a UOE steel pipe manufacturing method using the same, and more particularly, a UOE steel pipe having a wire diameter of 1.2 to 3.2 mmφ. The present invention relates to a material suitable for application to outer seam welding of a UOE steel pipe using a thin wire.

  The UOE steel pipe is a U press or O press, and after forming the steel plate into a cylindrical shape so that the ends in the width direction of the steel plate face each other, the outer groove 21 and the inner groove 22 of the groove portion 2 shown in FIG. As shown in FIGS. 5A and 5B, the cylindrical inner surface side (inner surface groove 22) and the outer surface side (outer surface groove 21) are welded in this order to form a steel pipe, and then plastic deformation is performed from the inner surface side with a pipe expanding device. Give and manufacture.

  FIG. 4 is a diagram for explaining the outer surface welding method, in which the pipe 1 is welded while being moved on the conveyor 9 so that the butt groove portion welded on the inner surface becomes the top portion. Welding is performed by feeding the welding wire 5 to the welding torch 8 with the feeding gear 3 from the wire pack 4 placed on the gantry above the conveyor 9. A detachable welding tip 81 is attached to the tip of the welding torch 8 and is appropriately replaced depending on the worn state.

  Conventionally, UOE steel pipe inner and outer surface welding is generally performed with a welding torch of about 2 to 5 electrodes (4 electrodes in the example of FIG. 4) and 1-pass welding with high heat input welding. As the steel plate as a raw material becomes stronger and thicker, it has become difficult to ensure HAZ toughness at severe low temperatures.

  Although the HAZ toughness is greatly improved by the low heat input welding, there is a concern that the amount of welding decreases accordingly, resulting in poor fusion in which the weld metals on the inner and outer surfaces do not overlap.

  Patent Document 1 relates to high current density submerged arc welding using a thin wire, and in order to achieve both a significant reduction in welding heat input and an increase in penetration depth, the current density is increased according to the electrode diameter and the penetration depth is increased. Although a submerged arc welding method is proposed, it is difficult to satisfy the recent HAZ toughness requirement due to insufficient reduction of welding heat input.

  Patent Document 2 relates to a submerged arc welding method for steel materials. As a submerged arc welding method at a high current density for flowing a high current through a thin wire, the necessary penetration depth is reduced by throwing arc energy in the plate thickness direction as much as possible. It is described that both the reduction of welding heat input and the deep penetration can be achieved by suppressing melting of the base material in the width direction of the steel material while ensuring.

JP-A-10-109171 JP 2006-272377 A

  However, in the case of the welding method characterized by deep penetration using the thin wire described in Patent Documents 1 and 2, a welding tip 81 that becomes the tip of the welding torch 8 as shown in FIGS. In some cases, the tip of the welding wire 5 is deflected at the wire protruding portion 10 of the welding wire 5 protruding from the wire. The cause of this deflection is considered to be due to the winding habit of the welding wire 5 wound in a coil shape.

  Since the welding method for deep penetration using a thin wire has a strong gouging force due to an arc, as shown in FIG. 6A, in the outer surface welding performed after inner surface welding, the wire protrusion 10 is deflected with respect to the groove. When deflected in a direction perpendicular to the weld line, the outer surface weld bead 12 becomes a penetration bent portion 13 as shown in FIG. 6B, and the fusion between the inner surface weld bead 11 and the outer surface weld bead 12 does not wrap, resulting in poor fusion. Occur.

  Accordingly, the present invention provides a welding torch capable of fusing an inner surface weld metal and an outer surface weld metal in a submerged arc welding method in which a high current is made to flow through a thin wire to achieve deep penetration. The purpose is to provide.

The inventors of the present invention diligently investigated the fusion failure of the inner and outer surface weld metals when the small diameter submerged arc welding method was applied to the seam welding of the UOE steel pipe, and obtained the following knowledge. In the description, the wire diameter of the thin wire is assumed to be 1.2 to 3.2 mmφ.
1. In the case of using a welding wire that has been wound by a straight wire straightening method using a straightening roller, there is no deflection due to bending of the tip of the welding wire at the wire protruding portion, and no melted bending portion is generated. However, in the case of a thin wire, it is difficult to remove curl by the straight wire straightening method using a straightening roller.
2. In the case of carbon dioxide arc welding, the protruding length of the welding wire from the welding tip is as short as about 10 mm, and even if there is a curl in the welding wire, there is little influence on the displacement of the welding point. However, in the case of submerged arc welding, the protruding length is often 30 mm or more, and the welding wire protruding from the tip of the welding tip is deflected in an arbitrary direction by the curl.
3. Since the protruding length from the welding tip affects the voltage of the welding conditions, if the welding tip is simply moved closer to the welding point, the predetermined voltage cannot be maintained even if the welding wire deflection becomes small, and it is healthy. A weld cannot be obtained.
4). Therefore, it is conceivable to guide the welding wire protruding from the tip of the welding tip so as not to be deflected while maintaining the projection length from the desired welding tip. Therefore, the material cannot be brought close to the welding point unless the material has excellent high temperature resistance.

The present invention has been made by further study based on the above knowledge, that is, the present invention,
1. It is made of an insulator having heat resistance, and includes a mounting portion to a welding tip of a welding torch for submerged arc welding and a guide portion for guiding a welding wire protruding from the welding tip, and is attachable to and detachable from the tip of the welding tip. A guide for feeding a welding wire.
2. The guide for feeding a welding wire according to 1, wherein a length of the guide portion is 5 to 15 mm, and a tip thereof is conical.
3. The welding wire feeding guide according to claim 1 or 2, wherein ceramic is used as the heat-resistant insulator.
4). A multi-multi-electrode submerged arc welding machine including a plurality of electrodes, wherein the welding wire feeding guide according to any one of 1 to 3 is attached to at least a welding torch of the first electrode. Multi-electrode submerged arc welding machine.
Using the multi-electrode submerged arc welding machine described in 5.4, seam welding is performed by using a welding wire having a diameter of 1.2 to 3.2 mm and a protruding length of the welding wire from the welding wire feeding guide of 15 to 25 mm. A method for producing a UOE steel pipe, characterized in that it is performed.

  According to the present invention, it is possible to apply a submerged arc welding method in which a high current is passed through a thin wire having a wire diameter of 1.2 to 3.2 mmφ for deep penetration by seam welding of a UOE steel pipe. A UOE steel pipe excellent in toughness is obtained, which is extremely useful in industry.

The fragmentary sectional view explaining the welding torch for submerged arc welding concerning one embodiment of the present invention. (A) is a figure explaining the lower structure and effect of the welding torch for submerged arc welding shown in FIG. 1, (b) is a figure explaining the condition by the lower structure of a prior art example, and its structure. The figure explaining the butt groove part of the seam welding of a UOE steel pipe. The figure explaining an outer surface welding method. It is a figure explaining welding of the butt groove part of the seam welding of a UOE steel pipe, (a) is an inner surface welding, (b) is a figure explaining an outer surface welding. The figure explaining the case where a welding wire deflect | deviates by welding of the butt groove part of UOE steel pipe seam welding, (a) is before outer surface welding, (b) is a figure explaining the penetration part after outer surface welding. It is a figure explaining the deflection | deviation of the welding wire in a wire protrusion part by the conventional small diameter submerged arc welding, (a) is a side view, (b) is a front view.

  The present invention attaches a welding wire feed guide made of an insulating material having heat resistance to the tip of the welding torch so that the tip of the welding wire coming out of the welding tip does not fluctuate, and protrudes from the welding tip The length of deflection in a free state is shortened.

  FIG. 1 is a partial sectional view illustrating a welding torch for submerged arc welding according to an embodiment of the present invention. In the figure, 8 is a welding torch, 81 is a welding tip, 82 is a lower member, and 83 is a wire inlet at the upper end. An upper member 84 has a welding wire feeding guide.

  The illustrated welding torch 8 comprises an upper member 83 and a lower member 82 having a wire inlet at the upper end, a welding tip 81 at the lower end of the lower member 82, and a welding wire feeding at the lower end of the welding tip 81. A guide 84 is attached. The welding tip 81 and the welding wire feeding guide 84 are detachable so that they can be replaced when worn.

  2 is an enlarged view (FIG. 2 (a)) of the substructure of the welding torch for submerged arc welding shown in FIG. 1, and a conventional example (FIG. 2 (b)) in which the welding wire feed guide 84 is not used. Shown in comparison.

  In the case of submerged arc welding, the protruding length D2 of the welding wire 5 from the welding tip 81 shown in FIG. 2 (b) is generally about 30 mm, but as a result, when a thin wire is used, Due to the curl, the length L2 at which the tip of the wire is deflected from the tip center of the welding tip 81 on the surface of the base material becomes about 3 mm.

  FIG. 2A shows a case where the welding wire feeding guide 84 of the present invention is attached to the stepped portion provided at the lower end of the welding tip 81. The welding wire feed guide 84 includes an attachment portion 85 to the welding tip, and a guide portion 86 having a length H for guiding the welding wire protruding from the welding tip. The protrusion length D1 of the welding wire 5 from the distal end portion of the welding wire feeding guide 84 is substantially equal to the length H of the guide portion 86 with respect to the protrusion length D2 of the welding wire 5 from the welding tip 81. Therefore, the length L1 at which the tip of the welding wire 5 is deflected from the tip center of the welding tip 81 on the surface of the base metal is shorter than the length L2 of the conventional example. 2A and 2B, the protruding length D2 of the welding wire 5 from the welding tip 81 is the same length.

  In the case of deep penetration welding using a thin wire, if the deflection amount from the tip center of the welding tip 81 at the tip of the wire is about 1.5 mm on the surface of the base material, it does not become a penetration bent portion, but an inner surface weld bead and an outer surface The weld bead penetration wraps.

  In the present invention, when the welding wire feeding guide 84 is attached to the welding tip 81, the protruding length D1 of the welding wire 5 from the tip of the welding wire feeding guide 84 is 15 to 25 mm. The height (length H) of the guide portion 86 of the welding wire feed guide 84 is determined. That is, when the welding wire protrusion length D2 from the welding tip 81 is 30 mm, the length H of the guide portion 86 of the welding wire feeding guide 84 is preferably 5 to 15 mm. When the length H of the guide portion 86 is less than 5 mm, the distance for guiding the welding wire 5 is short, so the effect of suppressing the deflection of the wire tip is small. On the other hand, when the length H exceeds 15 mm, the tip of the guide portion 86 is too close to the welded portion. As a result, the melted portion and the guide come into contact with each other and the guide is damaged, and the quality of the melted portion is affected. More preferably, it is 10-15 mm.

  A welding wire feeding guide is provided so that the welding point does not change when the welding wire feeding guide 84 is attached to the welding tip 81 and the energization point to the welding wire 5 changes (the welding voltage changes). 84 is made of an insulator. Further, since the welding wire feeding guide 84 is close to the molten pool and exposed to a high temperature, the material needs to be excellent in heat resistance, and it is desirable to use ceramic as a material having insulation and heat resistance. . For example, it is preferable to use reinforced alumina having heat resistance of 1800 ° C.

  The tip of the welding wire feeding guide 84 is preferably shaped so as not to disturb the flow of flux on the molten pool, and is shaped like a cone or an acute angle in the welding progress direction.

  According to the present invention, since the welding wire protrudes from a position closer to the groove than the welding wire feeding guide tip, the degree of deflection by the curl is suppressed, and a good welded portion is obtained.

  In the case of a multi-electrode submerged arc welding machine that performs deep penetration welding using a thin wire, since the deep penetration welding portion is formed using a thin wire for the first electrode, the welding wire feeding guide according to the present invention is at least It is preferable to use by attaching to the welding torch of the first electrode.

  Since the influence of the first electrode is very large on the bending of the melted portion, it is possible to prevent the melting and bending even if the welding wire feeding guide according to the present invention is used only for the first electrode.

  And, using such a submerged arc welding machine in which the welding wire feeding guide of the present invention is attached to a welding torch, the outer surface welding method shown in FIG. Even when a thin wire having a diameter of 2 to 3.2 mmφ is used, a UOE steel pipe excellent in HAZ toughness without melting and bending can be produced.

  In addition, although the above description described the case where the welding wire feeding guide of the present invention was applied to the outer surface welding of the UOE steel pipe, the present invention is not limited to this, the inner surface welding of the UOE steel pipe, It can also be applied to submerged arc welding to other objects.

  The outer surface seam welding of a UOE steel pipe having a total length of 12 m was performed by a four-electrode submerged arc welding machine in which the welding wire feeding guide according to the present invention was attached only to the first electrode. Here, a thin wire having a winding diameter of 750 mmφ and a wire diameter of 2.4 mmφ was used as the welding wire, and the wire protrusion length D2 from the welding tip was set to 30 mm.

  The welding wire feeding guide attached to the welding tip is made of reinforced alumina having heat resistance of 1800 ° C., and in the state attached to the welding tip, the guide portion length H is determined so that the wire protrusion length D1 is 20 mm, The mounting part was processed. A male screw was processed into the welding tip and a female screw was processed into the guide so that it could be removed.

  At this time, the distance L1 at which the tip of the welding wire protruding from the tip of the welding tip was deflected in the left-right direction with respect to the traveling direction from the weld line was measured to be ± 1.5 mm. And the sound weld part was able to be obtained, without the abnormality of a melt | dissolution generating.

  On the other hand, when the same welding was performed with a conventional four-electrode submerged arc welding machine (without a guide for feeding the welding wire), the deflection distance L2 in the left-right direction of the welding wire tip was ± 3 mm. And a melt | dissolution bending generate | occur | produced partially and the stable welding could not be performed.

DESCRIPTION OF SYMBOLS 1 Pipe 2 Groove part 21 Outer surface groove 22 Inner surface groove 3 Feed gear 4 Wire pack 5 Welding wire 8 Welding torch 81 Welding tip 82 Lower member 83 Upper member 84 Welding wire feeding guide 85 Attachment part 86 Guide part 9 Conveyor 10 Wire protrusion 11 Inner surface weld bead 12 Outer surface weld bead 13 Penetration curve

Claims (5)

An insulating material having heat resistance, and a guide portion for guiding the welding wire Extruded diameter 1.2~3.2mm the mounting portion of the welding tip of the welding torch for submerged arc welding from the welding tip, wherein The guide for welding wire feeding , wherein the guide portion is detachably installed only at the tip of the welding tip only on the first electrode of the multi-electrode submerged arc welder .   The guide for welding wire feeding according to claim 1, wherein the guide portion has a length of 5 to 15 mm and a tip of the guide portion is conical.   The welding wire feeding guide according to claim 1, wherein ceramic is used as the heat-resistant insulator. A multi-electrode submerged arc welding machine with a plurality of electrodes,
A multi-electrode submerged arc welding machine comprising a welding wire feeding guide according to any one of claims 1 to 3 attached to a welding torch of a first electrode .   The multi-electrode submerged arc welding machine according to claim 4, wherein a welding wire having a diameter of 1.2 to 3.2 mm is used, and a protruding length of the welding wire from the welding wire feeding guide is set to 15 to 25 mm to perform seam welding. A method for producing a UOE steel pipe, characterized in that it is performed.

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